Aqueous coating material, especially aqueous filler or protective base against stones

ABSTRACT

Aqueous coating material comprising (A) water-dispersible hydroxy-functional binder component containing urethane groups, (B) water-dispersible binder component containing urethane groups and blocked isocyanate groups, (C) water-dispersible amino resin, and optionally (D) water-dispersible hydroxy-functional polyester, the binder component (B) being preparable by (B1) preparing a polyurethane prepolymer containing isocyanate groups from at least one polyol and at least one polyisocyanate, (B2) reacting the polyurethane prepolymer (B1) containing isocyanate groups with a chain extender to give a hydroxyl-containing chain-extended polyurethane prepolymer, (B3) reacting the hydroxyl-containing chain-extended polyurethane prepolymer (B2) with at least one polyisocyanate to give a further polyurethane prepolymer containing isocyanate groups, and (B4) blocking some or all of the isocyanate groups of the chain-extended polyurethane prepolymer (B3) containing isocyanate groups with a blocking agent to give a polyurethane containing blocked isocyanate groups, and then, where appropriate, (B5) reacting remaining free isocyanate groups in the polyurethane (B4) with a chain extender.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. Ser. No. 10/018,155,filed on 10 Jan. 2002, which is a 371 National Stage Application ofPCT/EP00/06106, filed 30 Jun. 2000, which claims priority to DE 199 30555.2, filed 2 Jul. 1999. U.S. Ser. No. 10/018,155 is incorporatedherein by reference.

[0002] The invention relates to an aqueous coating material, especiallyan aqueous surfacer or antistonechip primer, comprising (A) awater-dispersible hydroxy-functional binder component containingurethane groups, (B) a water-dispersible binder component containingurethane groups and blocked isocyanate groups, (C) a water-dispersibleamino resin, (D) optionally, a water-dispersible hydroxy-functionalpolyester, and (E) optionally, customary coatings additives. Theinvention further relates to a process for preparing such a coatingmaterial and to the uses thereof.

[0003] The provision of stonechip-resistant coatings on metallicsubstrates is of particular importance in the field of motor vehicleproduction. Stonechip-resistant coatings are applied in particular inthe front area and in the underbody area of a motor vehicle body. Forreasons both economic and environmental, a coating material suitable forthis purpose ought to contain little or no organic solvents. Only (apartfrom powder coating materials) aqueous coating materials are suitablefor this purpose.

[0004] A surfacer or antistonechip primer is subject to a number ofrequirements. It must be bakeable at a temperature of 120-160° C. andafter baking at such temperatures must exhibit outstanding propertiessuch as high stonechip resistance (particularly the combination ofmultiple and single chipping), effective adhesion to the primer coat, acathodic electrode coat, for example, and to the base coat, good fillingproperties (masking of the structure of the substrate) at a coatthickness of 20-35 μm, and an excellent appearance in the finalclearcoat. The combination of these properties is difficult to realizeon account of the fact that they are in part divergent properties, whereimproving one property automatically results in a deterioration inanother property. Such divergent or contradictory properties are, forexample, very good resistance to multiple chipping and to singlechipping, low coat thickness and very good filling power/topcoatappearance, low baking temperature and very good topcoat appearance, andlow baking temperature and high adhesion.

[0005] A coating material of the composition specified at the outset isknown from the reference EP 0 427 028 B1. In this material, component(B) is the reaction product of a diisocyanate and a low molecular masspolyol. With the known coating material, not all of the abovementioneddivergent properties are obtained to a satisfactory extent. For asolventborne antistonechip primer, refer, for example, to the referenceDE 31 08 861 C2. Solventborne coating materials are unsatisfactory onenvironmental grounds alone. The reference DE 41 42 816 C1 discloses asurfacer for which the abovementioned components (A) and (B) are firstof all reacted with one another and then the reaction product is mixedwith a polyisocyanate and a melamine resin to give the application-readycoating material. Technically speaking, this is a comparativelylaborious preparation. Moreover, even with the known coating material,not all of the abovementioned divergent properties are realized to asufficient extent. Further stonechip protection compositions are known,for example, from the references DE 38 05 629 C1 and DE 195 04 947 A1.

[0006] In opposition to the prior art specified at the outset, thetechnical problem on which the invention is based is to specify acoating material with which the desired divergent properties mentionedare obtained in a way which, overall, meets all of the requirements.

[0007] To solve this technical problem, the invention teaches that thebinder component (B) specified at the outset is preparable by

[0008] (B1) preparing a polyurethane prepolymer containing isocyanategroups from a polyol or mixture of polyols and from a polyisocyanate ormixture of polyisocyanates,

[0009] (B2) reacting the polyurethane prepolymer (B1) containingisocyanate groups by means of a chain extender to give ahydroxyl-containing chain-extended polyurethane prepolymer,

[0010] (B3) reacting the hydroxyl-containing chain-extended polyurethaneprepolymer (B2) with a polyisocyanate or mixture of polyisocyanates togive a further polyurethane prepolymer containing isocyanate groups, and

[0011] (B4) blocking some or all of the isocyanate groups of thechain-extended polyurethane prepolymer (B3) containing isocyanate groupswith a blocking agent to give a polyurethane containing blockedisocyanate groups, and then, where appropriate,

[0012] (B5) reacting remaining free isocyanate groups in thepolyurethane (B4) with a chain extender.

[0013] Surprisingly, using the above-defined component (B) for use inaccordance with the invention in the coating material specified at theoutset, comprising components (A) and (C) and also, where appropriate,(D) and (E), gives a coating material which satisfies all of therequirements.

[0014] The binder component (B) for use in accordance with the inventionis obtainable by reacting, in a first process step, at least one polyolwith at least one polyisocyanate to give the polyurethane prepolymer(B1) containing isocyanate groups.

[0015] Examples of suitable polyols are saturated or olefinicallyunsaturated polyesterpolyols having a number-average molecular weight offrom 300 to 5000, preferably from 1000 to 2000, and in particular from1200 to 1600, which are prepared by reacting

[0016] sulfonated or unsulfonated saturated and/or unsaturatedpolycarboxylic acids or their esterifiable derivatives, together ifdesired with monocarboxylic acids, and

[0017] saturated and/or unsaturated polyols, together if desired withmonools.

[0018] Examples of suitable polycarboxylic acids are aromatic, aliphaticand cycloaliphatic polycarboxylic acids. Preference is given to usingaromatic and/or aliphatic polycarboxylic acids.

[0019] Examples of suitable aromatic polycarboxylic acids are phthalicacid, isophthalic acid, terephthalic acid, phthalic, isophthalic orterephthalic monosulfonate, or halophthalic acids, such as tetrachloro-and/or tetrabromophthalic acid, of which isophthalic acid isadvantageous and is therefore used with preference.

[0020] Examples of suitable acyclic aliphatic or unsaturatedpolycarboxylic acids are oxalic acid, malonic acid, succinic acid,glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid,sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid ordimer fatty acids or maleic acid, fumaric acid or itaconic acid, ofwhich adipic acid, glutaric acid, azelaic acid, sebacic acid, dimerfatty acids and maleic acid are advantageous and therefore used withpreference.

[0021] Examples of suitable cycloaliphatic and cyclic unsaturatedpolycarboxylic acids are 1,2-cyclobutanedicarboxylic acid,1,3-cyclobutanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid,1,3-cyclopentanedicarboxylic acid, hexahydrophthalic acid,1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,4-methylhexahydrophthalic acid, tricyclodecanedicarboxylic acid,tetrahydrophthalic acid or 4-methyltetrahydrophthalic acid. Thesedicarboxylic acids may be used both in their cis and in their trans formand also as a mixture of both forms.

[0022] Also suitable are the esterifiable derivatives of theabovementioned polycarboxylic acids, such as, for example, theirmonoesters or polyesters with aliphatic alcohols having from 1 to 4carbon atoms or hydroxy alcohols having from 1 to 4 carbon atoms.Moreover, it is also possible to use the anhydrides of theabovementioned polycarboxylic acids, where they exist.

[0023] If desired it is possible, together with the polycarboxylicacids, to use monocarboxylic acids too, such as benzoic acid,tert-butylbenzoic acid, lauric acid, isononanoic acid, fatty acids ofnaturally occurring oils, acrylic acid, methacrylic acid, ethacrylicacid or crotonic acid, for example. As monocarboxylic acid it ispreferred to use isononanoic acid.

[0024] Examples of suitable polyols are diols and triols, especiallydiols. Normally, triols are used in minor amounts alongside the diols inorder to introduce branches into the polyesterpolyols.

[0025] Suitable diols are ethylene glycol, 1,2- or 1,3-propanediol,1,2-, 1,3- or 1,4-butanediol, 1,2-, 1,3-, 1,4- or 1,5-pentanediol, 1,2-,1,3-, 1,4-, 1,5- or 1,6-hexanediol, neopentyl hydroxypivalate, neopentylglycol, diethylene glycol, 1,2-, 1,3- or 1,4-cyclohexanediol, 1,2-, 1,3-or 1,4-cyclohexanedimethanol, trimethylpentanediol,ethylbutylpropanediol, or the positionally isomeric diethyloctanediols.These diols may also be used per se for the preparation of thepolyurethanes (A) for inventive use.

[0026] Further examples of suitable diols are diols of the formula I orII:

[0027] in which R¹ and R² each represent an identical or differentradical and stand for an alkyl radical having from 1 to 18 carbon atoms,an aryl radical or a cycloaliphatic radical, with the proviso that R¹and/or R² may not be methyl;

[0028] in which R³, R⁴, R⁶ and R⁷ each represent identical or differentradicals and stand for an alkyl radical having from 1 to 6 carbon atoms,a cycloalkyl radical or an aryl radical and R⁵ represents an alkylradical having from 1 to 6 carbon atoms, an aryl radical or anunsaturated alkyl radical having from 1 to 6 carbon atoms, and n iseither 0 or 1.

[0029] Suitable diols I of the general formula I are all propanediols ofthe formula in which either R¹ or R² or R¹ and R² is not equal tomethyl, such as 2-butyl-2-ethylpropane-1,3-diol,2-butyl-2-methylpropane-1,3-diol, 2-phenyl-2-methylpropane-1,3-diol,2-propyl-2-ethylpropane-1,3-diol, 2-di-tert-butylpropane-1,3-diol,2-butyl-2-propylpropane-1,3-diol,1-dihydroxymethylbicyclo[2.2.1]heptane, 2,2-diethylpropane-1,3-diol,2,2-dipropylpropane-1,3-diol or 2-cyclohexyl-2-methylpropane-1,3-dioland others, for example.

[0030] As diols II of the general formula II it is possible, forexample, to use 2,5-dimethylhexane-2,5-diol, 2,5-diethylhexane-2,5-diol,2-ethyl-5-methylhexane-2,5-diol, 2,4-dimethylpentane-2,4-diol,2,3-dimethylbutane-2,3-diol, 1,4-(2′-hydroxypropyl)benzene and1,3-(2′-hydroxypropyl)benzene.

[0031] Of these diols, hexanediol and neopentyl glycol are particularlyadvantageous and are therefore used with particular preference.

[0032] The abovementioned diols may also be used per se for thepreparation of the polyurethane prepolymers (B1) containing isocyanategroups.

[0033] Examples of suitable trials are trimethylolethane,trimethylolpropane or glycerol, especially trimethylolpropane.

[0034] The abovementioned triols may also be used per se for thepreparation of the polyurethane prepolymers (B1) containing isocyanategroups (cf. the patent EP-A-0 339 433).

[0035] If desired, minor amounts of monools may be used as well.Examples of suitable monools are alcohols or phenols such as ethanol,propanol, n-butanol, sec-butanol, tert-butanol, amyl alcohols, hexanols,fatty alcohols, allyl alcohol or phenol.

[0036] Especially advantageous polyesterpolyols result if the monomersare selected from the group consisting of isophthalic acid, dimer fattyacids, and hexanediol.

[0037] The polesterpolyols may be prepared in the presence of smallamounts of an appropriate solvent as entrainer. Entrainers used include,for example, aromatic hydrocarbons, such as particularly xylene and(cyclo)aliphatic hydrocarbons, e.g., cyclohexane or methylcyclohexane.

[0038] Further examples of suitable polyols are polyesterdiols which areobtained by reacting a lactone with a diol. They are notable for thepresence of terminal hydroxyl groups and repeating polyester units ofthe formula —(—CO—(CHR⁸)_(m)—CH₂—O—)—. In this formula the index m ispreferably from 4 to 6 and the substituent R⁸=hydrogen, an alkyl,cycloalkyl or alkoxy radical. No one substituent contains more than 12carbon atoms. The total number of carbon atoms in the substituent doesnot exceed 12 per lactone ring. Examples thereof are hydroxycaproicacid, hydroxybutyric acid, hydroxydecanoic acid and/or hydroxystearicacid.

[0039] For the preparation of the polyesterdiols preference is given tothe unsubstituted epsilon-caprolactone, in which m has the value 4 andall R⁸ substituents are hydrogen. The reaction with lactone is startedby low molecular mass polyols such as ethylene glycol, 1,3-propanediol,1,4-butanediol or dimethylolcyclohexane. It is, however, also possibleto react other reaction components, such as ethylenediamine,alkyldialkanolamine or else urea, with caprolactone. Further suitablehigh molecular mass diols include polylactamdiols, prepared by reacting,for example, epsilon-caprolactam with low molecular mass diols.

[0040] Further examples of suitable polyols are polyetherpolyols,especially those having a number-average molecular weight of from 400 to5000, in particular from 400 to 3000. Highly suitable polyetherdiolsare, for example, polyetherdiols of the general formulaH—(O—(CHR⁹)_(o)—)_(p)OH, in which the substituent R⁹=hydrogen or is alower, unsubstituted or substituted alkyl radical, the index o=2 to 6,preferably 3 to 4, and the index p=2 to 100, preferably 5 to 50. Citedas particularly highly suitable examples are linear or branchedpolyetherdiols such as poly(oxyethylene) glycols, poly(oxypropylene)glycols and poly(oxybutylene) glycols.

[0041] The polyetherdiols should on the one hand not introduce excessiveamounts of ether groups, since otherwise the polyurethanes (B) forinventive use that are formed undergo incipient swelling in water. Onthe other hand, they may be used in amounts which ensures the nonionicstabilization of the polyurethanes (B). In that case they serve as thefunctional nonionic groups (b3) described below.

[0042] In order to ensure dispersibility of the binder component (B) foruse in accordance with the invention in an aqueous medium, not only arethe polyols incorporated but also compounds by means of whichstabilizing (potentially) ionic and/or nonionic functional groups areintroduced. Suitable groups of this kind are

[0043] (b1) functional groups which can be converted into cations byneutralizing agents and/or quaternizing agents, and/or cationic groups,

[0044] or

[0045] (b2) functional groups which can be converted into anions byneutralizing agents, and/or anionic groups,

[0046] and/or

[0047] (b3) nonionic hydrophilic groups.

[0048] Examples of suitable functional groups (b1) for inventive usewhich may be converted into cations by neutralizing agents and/orquaternizing agents are primary, secondary or tertiary amino groups,secondary sulfide groups or tertiary phosphine groups, especiallytertiary amino groups or secondary sulfide groups.

[0049] Examples of suitable cationic groups (b1) for inventive use areprimary, secondary, tertiary or tertiary sulfonium groups or quaternaryphosphonium groups, preferably quaternary ammonium groups or quaternaryammonium groups, tertiary sulfonium groups, but especially tertiarysulfonium groups.

[0050] Examples of suitable functional groups (b2) for inventive usewhich may be converted into anions by neutralizing agents are carboxylicacid, sulfonic acid or phosphonic acid groups, especially carboxylicacid groups.

[0051] Examples of suitable anionic groups (b2) for inventive use arecarboxylate, sulfonate or phosphonate groups, especially carboxylategroups.

[0052] Examples of suitable neutralizing agents for functional groups(b1) convertible into cations are organic and inorganic acids such asformic acid, acetic acid, lactic acid, dimethylolpropionic acid, citricacid, sulfuric acid, hydrochloric acid or phosphoric acid.

[0053] Examples of suitable neutralizing agents for functional groups(b2) convertible into anions are ammonia, ammonium salts, such asammonium carbonate or ammonium hydrogen carbonate, for example, and alsoamines, such as trimethylamine, triethylamine, tributylamine,dimethylaniline, diethylaniline, triphenylamine, dimethylethanolamine,diethylethanolamine, methyldiethanolamine, triethanolamine and the like,for example. The neutralization may take place in organic phase or inaqueous phase. A preferred neutralizing agent used isdimethylethanolamine.

[0054] The overall amount of neutralizing agent used in the coatingcomposition of the invention is chosen so that from 1 to 100equivalents, preferably from 50 to 90 equivalents, of the functionalgroups (b1) or (b2) of the polyurethane (A) for inventive use areneutralized.

[0055] Of these functional (potentially) ionic groups (b1) and (b2) andfunctional nonionic groups (b3), the (potentially) anionic groups (b2)are advantageous and are therefore used with particular preference.

[0056] The introduction of (potentially) anionic groups (b2) into thepolyurethane molecules takes place by way of the incorporation ofcompounds which contain in the molecule at least one isocyanate-reactivegroup and at least one group capable of forming anions; the amount to beused may be calculated from the target acid number.

[0057] Examples of suitable compounds of this kind are those whichcontain two isocyanate-reactive groups in the molecule. Suitableisocyanate-reactive groups are, in particular, hydroxyl groups, and alsoprimary and/or secondary amino groups. Accordingly, it is possible, forexample, to use alkanoic acids having two substituents on the alphacarbon atom. The substituent may be a hydroxyl group, an alkyl group or,preferably, an alkylol group. These alkanoic acids have at least one, ingeneral from 1 to 3, carboxyl groups in the molecule. They have from 2to about 25, preferably from 3 to 10, carbon atoms. Examples of suitablealkanoic acids are dihydroxypropionic acid, dihydroxysuccinic acid anddihydroxybenzoic acid. One particularly preferred group of alkanoicacids are the alpha,alpha-dimethylolalkanoic acids of the generalformula R¹⁰—C(CH₂OH)₂COOH, in which R¹⁰ stands for a hydrogen atom or analkyl group having up to about 20 carbon atoms. Examples of especiallysuitable alkanoic acids are 2,2-dimethylolacetic acid,2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid and2,2-dimenthylolpentanoic acid. The preferred dihydroxyalkanoic acid is2,2-dimethylolpropionic acid. Examples of compounds containing aminogroups are alpha,alpha-diaminovaleric acid, 3,4-diaminobenzoic acid,2,4-diaminotoluenesulfonic acid and 2,4-diaminodiphenyl ether sulfonicacid.

[0058] Nonionic stabilizing poly(oxyalkylene) groups (b3) may beintroduced as lateral or terminal groups into the polyurethanemolecules. For this purpose it is possible, for example, to usealkoxypoly(oxyalkylene) alcohols having the general formulaR¹¹O—(—CH₂—CH¹²—O—)_(r) H in which R¹¹ stands for an alkyl radicalhaving from 1 to 6 carbon atoms, R¹² stands for a hydrogen atom or analkyl radical having from 1 to 6 carbon atoms and the index r stands fora number between 20 and 75. (cf. the patents EP-A-0 354 261 or EP-A-0424 705).

[0059] Suitable polyisocyanates include in principle all customary andknown aliphatic, cycloaliphatic, aliphatic-cycloaliphatic, aromatic,aliphatic-aromatic and/or cycloaliphatic-aromatic polyisocyanates andpolyisocyanate adducts that are used in the paints sector, and are alsoreferred to as paint polyisocyanates.

[0060] Examples of suitable polyisocyanates are isophorone diisocyanate(=5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane),5-isocyanato-1-(2-isocyanatoeth-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane,5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane,1-isocyanato-2-(3-isocyanatoprop-1-yl)-cyclohexane,1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane,1-isocyanato-2-(4-isocyanatobut-1-yl)cyclohexane,1,2-diisocyanatocyclobutane, 1,3-diisocyanatocyclobutane,1,2-diisocyanatocyclopentane, 1,3-diisocyanatocyclopentane,1,2-diisocyanatocyclohexane, 1,3-diisocyanatocyclohexane,1,4-diisocyanatocyclohexane, dicyclohexylmethane 2,4′-diisocyanate,dicyclohexylmethane 4,4′-diisocyanate, liquid dicyclohexylmethanae4,4′-diisocyanate with a trans/trans content of up to 30% by weight,preferably 25% by weight, and in particular 20% by weight, obtainable byphosgenation of isomer mixtures of bis(4-aminocyclohexyl)methane or byfractional crystallization of commercialbis(4-isocyanatocyclohexyl)methane in accordance with the patentsDE-A-44 14 032, GB-A-1220717, DE-A-16 18 795 or DE-A-17 93 785;trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylenediisocyanate, hexamethylene diisocyanate, ethylethylene diisocyanate,trimethylhexane diisocyanate, heptamethylene diisocyanate ordiisocyanates derived from dimer fatty acids, such as are sold under thecommercial designation DDI 1410 by Henkel and described in the patentsWO 97/49745 and WO 97/49747, especially2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentylcyclohexane, 1,2-, 1,4- or1,3-bis(isocyanatomethyl)cyclohexane, 1,2-, 1,4- or1,3-bis(2-isocyanatoeth-1-yl)cyclohexane,1,3-bis(3-isocyanatoprop-1-yl)cyclohexane, 1,2-, 1,4- or1,3-bis(4-isocyanatobut-1-yl)cyclohexane, m-tetramethylxylylenediisocyanate (=1,3-bis(2-isocyanatoprop-2-yl)benzene or tolylenediisocyanate.

[0061] Examples of suitable polyisocyanate adducts are polyurethaneprepolymers containing isocyanate groups, which may be prepared byreacting polyols with an excess of polyisocyanates and are preferably oflow viscosity. It is also possible to use polyisocyanates containingisocyanurate, biuret, allophanate, iminooxadiazinedione, urethane, ureacarbodiimide and/or uretdione groups. Polyisocyanates containingurethane groups, for example, are obtained by reacting some of theisocyanate groups with polyols, such as trimethylolpropane and glycerol,for example. In this case it is preferred to use the polyisocyanatesdescribed in detail above.

[0062] Very particular preference is given to using mixtures ofpolyisocyanate adducts containing uretdione and/or isocyanurate groupsand/or allophanate groups, especially isocyanurates, based in particularon hexamethylene diisocyanate, such as are formed by catalyticoligomerization of hexamethylene diisocyanate using appropriatecatalysts. The polyisocyanate constituent may otherwise also consist ofany desired mixtures of the free polyisocyanates exemplified.

[0063] In the preparation of the polyurethane prepolymer (B1) containingisocyanate groups, the isocyanate groups are preferably employed in amolar excess over the hydroxyl groups. It is of advantage in accordancewith the invention if the ratio of hydroxyl groups in the polyols toisocyanate groups in the polyisocyanates is from 1:6 to 1:1.1,preferably from 1:5 to 1:1.2, and in particular from 1:4 to 1:1.3. If itis ensured otherwise that the resulting polyurethane prepolymer (B1)contains isocyanate groups, it is also possible to employ the hydroxylgroups in excess.

[0064] In accordance with the invention, in a second process step, thepolyurethane prepolymer (B1) containing isocyanate groups is chainextended with a suitable chain extender, so that hydroxyl groups result.Suitable chain extenders include: at least one polyol having afunctionality of from 2 to 4, at least one polyamine and/or at least onealkanolamine. The use of polyols, polyamines and amino alcohols leads tothe molecular weight increase of the polyurethanes (B).

[0065] Suitable polyols for the chain extension are polyols having up to36 carbon atoms per molecule such as ethylene glycol, diethylene glycol,triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol,1,2-butylene glycol, 1,6-hexanediol, trimethylolpropane, castor oil orhydrogenated castor oil, ditrimethylolpropane ether, pentaerythritol,1,2-cyclohexanediol, 1,4-cyclohexanedimethanol, bisphenol A, bisphenolF, neopentyl glycol, neopentyl glycol hydroxypivalate, hydroxyethylatedor hydroxypropylated bisphenol A, hydrogenated bisphenol A or mixturesthereof (cf. also patents EP-A-0 339 433, EP-A-0 436 941, EP-A-0 517707).

[0066] Examples of suitable polyamines have at least two primary and/orsecondary amino groups. Polyamines are essentially alkylene polyamineshaving from 1 to 40 carbon atoms, preferably from about 2 to 15 carbonatoms. They may carry substituents which have no hydrogen atoms that arereactive with isocyanate groups. Examples are polyamines having a linearor branched aliphatic, cycloaliphatic or aromatic structure andcontaining at least two primary amino groups.

[0067] As diamines, mention may be made of hydrazine, ethylenediamine,propylenediamine, 1,4-butylenediamine, piperazine,1,4-cyclohexyldimethylamine, 1,6-hexamethylenediamine,trimethylhexamethylenediamine, menthanediamine, isophoronediamine(1-amino-3-amino-methyl-3,5,5-trimethylcyclohexane),4,4′-diaminodicyclohexylmethane, 4,4′-diaminodicyclohexane,m-xylylenediamine, p-xylylenediamine, or isomeric octanediamines.Preferred diamines are hydrazine, alkyl or cycloalkyldiamines such aspropylenediamine and isophoronediamine.

[0068] It is also possible to use polyamines which contain more than twoamino groups in the molecule. In these cases, however, it must beensured—for example, by using monoamines as well—that crosslinkedpolyurethane resins are not obtained. Polyamines of this kind which canbe used are diethylenetriamine, triethylenetetramine, dipropylenediamineand dibutylenetriamine. An example to be mentioned of a monoamine isethylhexylamine (cf. also the patent EP-A-0 089 497).

[0069] Examples of suitable amino alcohols are ethanolamine,methylethanolamine, diisopropylamine, diethanolamine,N-methyldiethanolamine, hydroxyethoxyethylamine, polyetheraminols,aminomethylpropanol, trishydroxymethyl-aminomethane or triethanolamine.

[0070] Of these, the polyols having a functionality of 3 to 4 and/or theamino alcohols which contain at least two hydroxyl groups, especiallydiethanolamine, are of particular advantage and are therefore used withparticular preference in accordance with the invention. The resultinghydroxyl-containing, chain-extended polyurethane prepolymer (B2) isreacted in a third process step with at least one polyisocyanate to givea further polyurethane prepolymer (B3) containing isocyanate groups.

[0071] Examples of suitable polyisocyanates are those described above.

[0072] In accordance with the invention, the polyurethane prepolymer(B3) containing isocyanate groups is reacted in a fourth process stepwith a blocking agent, so that some or all of its isocyanate groupsbecome masked or blocked and the polyurethane (B4) containing blockedisocyanate groups, i.e., the binder component (B) for use in accordancewith the invention, is the result.

[0073] Examples of suitable blocking agents are the blocking agentsknown from U.S. Pat. No. 4,444,954:

[0074] i) phenols such as phenol, cresol, xylenol, nitrophenol,chlorophenol, ethylphenol, t-butylphenol, hydroxybenzoic acid, esters ofthis acid, or 2,5-di-tert-butyl-4-hydroxytoluene;

[0075] ii) lactams, such as ε-caprolactam, δ-valerolactam,γ-butyrolactam or β-propiolactam;

[0076] iii) active methylenic compounds, such as diethyl malonate,dimethyl malonate, ethyl or methyl acetoacetate, or acetylacetone;

[0077] iv) alcohols such as methanol, ethanol, n-propanol, isopropanol,n-butanol, isobutanol, t-butanol, n-amyl alcohol, t-amyl alcohol, laurylalcohol, ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, diethylene glycol monomethylether, diethylene glycol monoethyl ether, propylene glycol monomethylether, methoxymethanol, glycolic acid, glycolic esters, lactic acid,lactic esters, methylolurea, methylolmelamine, diacetone alcohol,ethylenechlorohydrin, ethylenebromohydrin, 1,3-dichloro-2-propanol,1,4-cyclohexyldimethanol or acetocyanohydrin;

[0078] v) mercaptans such as butyl mercaptan, hexyl mercaptan, t-butylmercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol,methylthiophenol or ethylthiophenol;

[0079] vi) acid amides such as acetoanilide, acetoanisidinamide,acrylamide, methacrylamide, acetamide, stearamide or benzamide;

[0080] vii) imides such as succinimide, phthalimide or maleimide;

[0081] viii) amines such as diphenylamine, phenylnaphthylamine,xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine,butylamine, dibutylamine or butylphenylamine;

[0082] ix) imidazoles such as imidazole or 2-ethylimidazole;

[0083] x) ureas such as urea, thiourea, ethyleneurea, ethylenethioureaor 1,3-diphenylurea;

[0084] xi) carbamates such as phenyl N-phenylcarbamate or 2-oxazolidone;

[0085] xii) imines such as ethyleneimine;

[0086] xiii) oximes such as acetone oxime, formaldoxime, acetaldoxime,acetoxime, methyl ethyl ketoxime, diisobutylketoxime, diacetylmonoxime,benzophenone oxime or chlorohexanone oximes;

[0087] xiv) salts of sulfurous acid such as sodium bisulfite orpotassium bisulfite;

[0088] xv) hydroxamic esters such as benzyl methacrylohydroxamate (BMH)or allyl methacrylohydroxamate; or

[0089] xvi) substituted pyrazoles, imidazoles or triazoles; and also

[0090] xvii) mixtures of these blocking agents, especiallydimethylpyrazole and triazoles, malonic esters and acetoacetic esters,or dimethylpyrazole and succinimide.

[0091] The blocking agents are selected so that the blocked isocyanategroups only undergo deblocking, and enter into crosslinking reactions,in precisely the temperature range within which the thermal crosslinkingof the coating material of the invention is to take place, in particularin the temperature range from 120 to 160° C.

[0092] Of the blocking agents described in detail above, the oximesxiii) in particular meet the aforementioned condition, so that they areused with particular preference in accordance with the invention. Ofthese, in turn, the ketoximes, especially methyl ethyl ketoxime, offervery particular advantages and are therefore used with very particularpreference.

[0093] The blocking agents are preferably employed in stoichiometricamounts.

[0094] Where free isocyanate groups are still present in the resultingblocked polyurethane (B4), they are reacted in an optional fifth processstep with at least one of the chain extenders described in detail above.

[0095] In terms of its method, the preparation of the binder component(B) for use in accordance with the invention has no special features butinstead takes place with the customary and known methods of preparingpolyurethanes preferably in an optionally water-miscible organic solventor solvent mixture which is not reactive toward isocyanates. Examples ofsuitable solvents are ketones such as methyl ethyl ketone or methylisobutyl ketone or cyclic amides such as N-methylpyrrolidone.

[0096] The binder component (B) for inventive use is present in thecoating material of the invention advantageously in an amount of from 1to 50%, preferably from 2 to 30%, with very particular preference from2.5 to 20%, and in particular from 3 to 10%, by weight based in eachcase on the solids content of the coating material of the invention.

[0097] For its use as intended, the binder component (B) for inventiveuse is dispersed in an aqueous medium and, if desired, the organicsolvents are removed by distillation.

[0098] The aqueous medium comprises substantially water. In this contextthe aqueous medium may already contain the further components of thecoating material of the invention that are described in detail below,(A), (C), (D) and/or (E) and/or, in minor amounts, other dissolvedsolid, liquid or gaseous, organic and/or inorganic substances of lowand/or high molecular mass. For the purposes of the present invention,the term “minor amount” refers to an amount which does not remove theaqueous nature of the aqueous medium.

[0099] The aqueous medium may also, however, comprise straight water.

[0100] It is of advantage in accordance with the invention to usestraight water. Further advantages result if the solids content of theresulting dispersion of the binder component (B) for inventive use isfrom 10 to 60%, preferably from 20 to 55%, and in particular from 25 to50%, by weight based in each case on the polyurethane dispersion (B).

[0101] As a further essential constituent the coating material of theinvention comprises the water-dispersible, hydroxy-functional bindercomponent (A) containing urethane groups.

[0102] A binder component (A) which can be used in the context of theinvention is preparable, for example, by reacting a polyol or mixture ofpolyols having a number-average molecular weight of from 100 to 5000,preferably from 150 to 2000, with a polyisocyanate or mixture ofpolyisocyanates, the structure and proportions of the polyol andpolyisocyanate being selected subject to the proviso that the bindercomponent (A) preferably has an OH number of from 30 to 160, morepreferably from 60 to 110.

[0103] Examples of suitable polyols and polyisocyanates are thosedescribed in detail above.

[0104] It is preferred if the polyol used to prepare the bindercomponent (A) is a polyesterpolyol which preferably has a number-averagemolecular weight of from 250 to 5000, most preferably from 350 to 2000.Advantageously, the monomers for preparing such a polyesterpolyol areflexibilizing. Flexibilizing monomers may be selected, for example, fromthe group consisting of “adipic acid, dimer fatty acids and hexanediol”.

[0105] Advantageous binder components (A) are obtained if use is alsomade of the compounds described in detail above by means of whichstabilizing (potentially) ionic and/or nonionic functional groups areintroduced, neutralizing agents and/or chain extenders.

[0106] In terms of its method, the preparation of the binder component(A) for use in accordance with the invention has no special features butinstead takes place with the customary and known methods of preparingpolyurethanes preferably in an optionally water-miscible organic solventor solvent mixture which is not reactive toward isocyanates. Examples ofsuitable solvents are ketones such as methyl ethyl ketone or methylisobutyl ketone or cyclic amides such as N-methylpyrrolidone.

[0107] The binder component (A) for inventive use is present in thecoating material of the invention advantageously in an amount of from 1to 70%, preferably from 2 to 50%, with very particular preference from 3to 40%, and in particular from 5 to 30%, by weight based in each case onthe solids content of the coating material of the invention.

[0108] For its use as intended, the binder component (A) for inventiveuse is dispersed in an aqueous medium and, if desired, the organicsolvents are removed by distillation.

[0109] The aqueous medium comprises substantially water. In this contextthe aqueous medium may already contain the further components of thecoating material of the invention that are described in detail below,(C), (D) and/or (E), the above-described binder component (B) forinventive use and/or, in minor amounts, other dissolved solid, liquid orgaseous, organic or inorganic substances of low and/or high molecularmass.

[0110] It is of advantage in accordance with the invention to usestraight water. Further advantages result if the solids content of theresulting dispersion of the binder component (A) for inventive use isfrom 10 to 60%, preferably from 20 to 55%, and in particular from 25 to50%, by weight based in each case on the polyurethane dispersion (A).

[0111] As component (C) it is possible to use any water-dilutable aminoresin. Suitable in this context is any amino resin suitable forsurfacers, topcoat materials or transparent clearcoat materials, or amixture of such amino resins, especially melamine-formaldehyde resinswhich are reactive toward OH groups at temperatures from 100° C. to 180°C., preferably from 120 to 160° C. For further details, refer to RömppLexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, page 29,“Amino resins”, and the textbook “Lackadditive” [Additives for coatings]by Johan Bieleman, Wiley-VCH, Weinheim, N.Y., 1998, pages 242 ff., or tothe book “Paints, Coatings and Solvents”, second completely revisededition, edit. D. Stoye and W. Freitag, Wiley-VCH, Weinheim, N.Y., 1998,pages 80 ff. Also suitable are the customary and known water-dilutableamino resins some of whose methylol and/or alkoxymethyl groups have beendefunctionalized by means of carbamate or allophanate groups. Aminoresins of this kind are described, for example, in the patents U.S. Pat.No. 4,710,542 and EP-B-0 245 700 and also in the article by B. Singh andcoworkers, “Carbamylmethylated Melamines, Novel Crosslinkers for theCoatings Industry” in Advanced Organic Coatings Science and TechnologySeries, 1991, volume 13, pages 193 to 207.

[0112] The water-dilutable amino resin (C) for inventive use is presentin the coating material of the invention advantageously in an amount offrom 1 to 50%, more preferably from 2 to 40%, with particular preferencefrom 3 to 30%, and in particular from 4 to 20%, by weight based in eachcase on the solids content of the coating material of the invention.

[0113] The binder component (B) which can be used optionallyadvantageously has the following properties: number-average molecularweight of up to 5000, preferably from 500 to 3000, and OH number ofbetween 50 and 300, preferably between 100 and 250. It is advantageousto use a component (D) which is composed at least in part of anepoxy-resin-modified, water-dilutable polyester preparable by

[0114] (D1) using

[0115] (D1.1) at least one polycarboxylic acid containing at least threecarboxyl groups, or a reactive derivative of this acid, and/or

[0116] (D1.2) at least one polyol containing at least one carboxyl groupand

[0117] (D1.3) at least one polycarboxylic acid containing two carboxylgroups, or a reactive derivative of this acid, and

[0118] (D1.4) at least one polyol

[0119] at least 10 mol %, preferably 30-70 mol %, of the components(D1.1), (D1.2), (D1.3) and (D1.4) used (based on(D1.1)+(D1.2)+(D1.3)+(D1.4)=100 mol %) containing at least one(cyclo)aliphatic structural element containing at least six carbon atoms

[0120] to synthesize a polyester which has a number-average molecularweight of less than 2000, preferably from 500 to 1500, an acid number offrom 35 to 240, preferably from 50 to 120, an OH number of from 56 to320, preferably from 80 to 200, and in which all (D1.1) and (D1.3)components are incorporated by condensation via at least two carboxylgroups, and

[0121] (D2) then reacting this polyester thus obtained with from 0.3 to1.5, preferably from 0.5 to 1.0, equivalents per polyester molecule

[0122] (D2.1) of an epoxy resin which has an epoxide equivalent weightof from 170 to 1000, preferably from 170 to 500, and is based on abisphenol, preferably bisphenol A, and/or

[0123] (D2.2) a derivative of this epoxy resin that contains at leastone epoxide group per molecule

[0124] under reaction conditions in which substantially only carboxylgroups react with epoxide groups, to give an epoxy-resin-modifiedpolyester, which following

[0125] (D3) neutralization of at least some of the free carboxyl groupsis present in water-dilutable form.

[0126] A polyester of this kind is known from the reference EP 0 269 828B1, to which reference is made for further details.

[0127] The carboxyl groups of the polyester are supplied by components(D1.1) and/or (D1.2) . The polyester may be synthesized using thecarboxyl group suppliers (D1.1) or (D1.2) alone or using a mixture ofcomponents (D1.1) and (D1.2).

[0128] Taking into account the abovementioned requirements, it ispossible in principle as component (D1.1) to use any polycarboxylic acidwhich contains at least three carboxyl groups and is suitable forpreparing polyesters, or a reactive derivative (e.g., anhydride, esteror halide) or a mixture of such acids and/or acid derivatives. Examplesthat may be mentioned include trimellitic acid, trimesic acid(1,3,5,-benzenetricarboxylic acid), pyromellitic acid and trimeric fattyacids. Trimellitic acid is used with preference.

[0129] Taking into account the abovementioned requirements, it ispossible in principle to use as component (D1.2) any carboxyl-containingpolyol suitable for preparing polyesters, or a mixture of such polyols,a polyol being understood to be an organic compound which carries atleast two hydroxyl groups. Advantageously, dimethylolpropionic acid isused as (D1.2) component.

[0130] Taking into account the abovementioned requirements, it ispossible in principle as component (D1.3) to use any polycarboxylic acidcontaining two carboxyl groups which is suitable for preparingpolyesters, and/or a reactive derivative (e.g., anhydride, ester orhalide) or a mixture of such acids and/or acid derivatives. Examples ofsuitable acids that may be mentioned are: phthalic acid, isophthalicacid, terephthalic acid, fumaric acid, maleic acid,endomethylenetetrahydrophthalic acid, succinic acid, adipic acid,suberic acid, azelaic acid, sebacic acid and dimeric fatty acids.Preference is given to using phthalic acid, isophthalic acid, adipicacid, and dimeric fatty acids.

[0131] Taking into account the abovementioned requirements, it ispossible in principle as component (D1.4) to use any polyol suitable forpreparing polyesters, or a mixture of polyols, a polyol being understoodto be an organic compound which carries at least two hydroxyl groups.Examples of suitable polyols are ethylene glycol, propanediols,butanediols, pentanediols. Neopentyl glycol, hexanediols, diethyleneglycol, glycerol, trimethylolethane, trimethylolpropane,pentaerythritol, dipentaerythritol, neopentyl glycol hydroxypivalate,2-methyl-2-propyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, and2,2,5-trimethyl-1,6-hexanediol. Preference is given to using neopentylglycol, 1,6-hexanediol, and neopentyl glycol hydroxypivalate.

[0132] The epoxy resins (D2.1) based on a bisphenol, preferablybisphenol A, generally comprise reaction products of bisphenols withepichlorohydrin. These epoxy resins are to have an epoxide equivalentweight of from 170 to 1000, preferably from 170 to 500, and to containpreferably on average from one to two, with particular preference two,epoxide groups per molecule.

[0133] It is also possible to use derivatives (D2.2) of these epoxyresins that contain at least one epoxide group per molecule. Suitablederivatives which may be used are reaction products, containing at leastone epoxide group per molecule, of the abovementioned epoxy resins and a(cyclo)aliphatic monocarboxylic or polycarboxylic acid, preferably amonocarboxylic or polycarboxylic acid having a (cyclo)aliphaticstructural element containing at least six carbon atoms. The derivativesmay be prepared by reacting the epoxy resins in question with, forexample, polymeric—preferably dimeric—fatty acids, adipic acid, azelaicacid, dodecanedicarboxylic acid, long-chain monocarboxylic acids,tetrahydrophthalic acid or hexahydrophthalic acid, so as to givereaction products which still contain at least one epoxide group permolecule.

[0134] Very particularly preferred water-dilutable polyesters areobtained if the polyester synthesized in stage (D1) was reacted withfrom 0.3 to 1.5, preferably from 0.5 to 1.0, equivalents per polyestermolecule of a reaction product (D2.2) containing at least one epoxidegroup per molecule, being the reaction product of an epoxy resin basedon a bisphenol, preferably bisphenol A, having an epoxide equivalentweight of from 170 to 1000, preferably from 170 to 500, and a(cyclo)aliphatic monocarboxylic or polycarboxylic acid containing a(cyclo)aliphatic structural element containing at least 18 carbon atoms,preferably a polymeric fatty acid, in particular a dimeric fatty acid.

[0135] Reaction between the polyester synthesized in stage (D1) with theepoxy resin or epoxy resin derivative (D2.1) and/or (D2.2) must beconducted such that essentially only the carboxyl groups of thepolyester (D1) are reacted with the epoxide groups of the epoxy resin(D2) and such that competing reactions, such as the reaction of hydroxylgroups with epoxide groups, for example, proceed only to a minor extent.

[0136] Examples of suitable reaction conditions are as follows: reactiontemperature 25-180° C., preferably 80-160° C. The reaction may beconducted in an inert solvent or in bulk and is advantageously catalyzedby basic catalysts, such as tertiary amines, for example.

[0137] Following neutralization (D3) of at least some of the carboxylgroups present in the epoxy-resin-modified polyester (D) using basiccompounds, such as ammonia, aliphatic secondary and tertiary amines,such as diisopropanolamine, dimethyl- and diethylaminoethanol and alsotrimethyl-, triethyl- and tripropylamine, preferably tertiary amines,the epoxy-resin-modified polyester (D) is present in water-dilutableform.

[0138] The dispersion of the polyester (D) in an aqueous medium takesplace as described above for the binder component (A) and (B) . In thiscase, advantageously, the same or approximately the same solids contentsare set.

[0139] In the coating material of the invention the polyester (D) may bepresent in an amount of from 1 to 50%, preferably from 2 to 40%, withparticular preference from 3 to 30%, and in particular from 5 to 20%, byweight based in each case on the solids content of the coating materialof the invention.

[0140] The coating material of the invention may further comprisecustomary coatings additives (E) in effective amounts. The nature andamount of the additives (E) are guided primarily by the intended use ofthe coating material of the invention. It is advantageous that theseadditives (E) are not volatile under the processing and applicationconditions of the coating material of the invention.

[0141] Where the coating material of the invention is used as topcoatmaterial or aqueous basecoat material, it comprises color and/or effectpigments (E) in customary and known amounts. The pigments (E) mayconsist of organic or inorganic compounds and may impart effect and/orcolor. The coating material of the invention therefore ensures, owing tothis large number of appropriate pigments (E), a universal breadth ofuse of the coating materials and permits the realization of a largenumber of color shades and optical effects.

[0142] As effect pigments (E) it is possible to use metal flake pigmentssuch as commercially customary aluminum bronzes, aluminum bronzeschromated in accordance with DE-A-36 36 183, and commercially customarystainless steel bronzes, and also nonmetallic effect pigments, such aspearlescent pigments and interference pigments, for example. Examples ofsuitable inorganic color pigments (E) are titanium dioxide, iron oxides,Sicotrans yellow and carbon black. Examples of suitable organic colorpigments are Indanthrene blue, Cromophthal red, Irgazine orange, andHeliogen green.

[0143] Furthermore, the coating material of the invention may compriseorganic and inorganic fillers (E) in customary and known, effectiveamounts. Examples of suitable fillers are titanium dioxide, carbonblack, graphite, chalk, calcium sulfates, barium sulfate, silicates suchas talc or kaolin, silicas such as Aerosil®, oxides such as aluminumhydroxide, iron oxides or magnesium hydroxide, or organic fillers suchas textile fibers, cellulose fibers, polyethylene fibers or wood flour.For further details, refer to Römpp Lexikon Lacke und Druckfarben, GeorgThieme Verlag, 1998, pages 250 ff., “Fillers”.

[0144] The coating materials of the invention that are used to producesurfacers or antistonechip primers contain these pigments and/or fillers(E) advantageously in an amount of from 10 to 80%, preferably from 15 to70%, with particular preference from 20 to 65%, and in particular from25 to 60%, by weight based in each case on the overall solids content ofthe inventive coating material.

[0145] The abovementioned additives (E) are omitted if the coatingmaterials of the invention are used as clearcoat materials.

[0146] Examples of suitable additives (E) which may be present both inthe inventive clearcoat materials and also in the topcoat, aqueousbasecoat materials and surfacers and antistonechip primers are

[0147] UV absorbers;

[0148] free-radical scavengers;

[0149] crosslinking catalysts;

[0150] slip additives;

[0151] polymerization inhibitors;

[0152] defoamers;

[0153] emulsifiers, especially nonionic emulsifiers such as alkoxylatedalkanols and polyols, phenols and alkylphenols, or anionic emulsifierssuch as alkali metal salts or ammonium salts of alkanecarboxylic acids,alkanesulfonic acids, and sulfo acids of alkoxylated alkanols andpolyols, phenols and alkylphenols;

[0154] wetting agents such as siloxanes, fluorine compounds, carboxylicmonoesters, phosphoric esters, polyacrylic acids and their copolymers,or polyurethanes;

[0155] adhesion promoters;

[0156] leveling agents;

[0157] film formation auxiliaries such as cellulose derivatives;

[0158] flame retardants;

[0159] low molecular mass, oligomeric, and high molecular mass reactivediluents which are able to participate in the thermal crosslinking,especially polyols such as tricyclodecanedimethanol, dendrimericpolyols, hyperbranched polyesters, polyols based on metathesis oligomersor branched alkanes having more than eight carbon atoms in the molecule;

[0160] high-boiling organic solvents (“long solvents”);

[0161] rheology control additives, such as those known from the patentsWO 94/22968, EP-A-0 276 501, EP-A-0 249 201 or WO 97/12945; crosslinkedpolymeric microparticles, such as are disclosed, for example, in EP-A-0008 127; inorganic phyllosilicates such as aluminum magnesium silicates,sodium magnesium phyllosilicates and sodium magnesium fluorine lithiumphyllosilicates of the montmorillonite type; silicas such as Aerosils;or synthetic polymers containing ionic and/or associative groups such aspolyvinyl alcohol, poly (meth)acrylamide, poly(meth)acrylic acid,polyvinylpyrrolidone, styrene-maleic anhydride copolymers orethylene-maleic anhydride copolymers and their derivatives, orhydrophobically modified ethoxylated urethanes or polyacrylates; or

[0162] crosslinking agents such as compounds or resins containinganhydride groups, compounds or resins containing epoxide groups,tris(alkoxycarbonyl-amino) triazines, compounds or resins containingcarbonate groups, blocked and/or nonblocked polyisocyanates,beta-hydroxyalkylamides, and also compounds containing on average atleast two groups capable of transesterification, examples being reactionproducts of malonic diesters and polyisocyanates or of esters andpartial esters of polyhydric alcohols of malonic acid withmonoiso-cyanates, such as are described in the European patent EP-A-0596 460.

[0163] Further examples of suitable coatings additives are described inthe textbook “Lackadditive” [Additives for coatings] by Johan Bieleman,Wiley-VCH, Weinheim, N.Y., 1998.

[0164] Where used, these additives (E), which may be present not only inthe clearcoat materials of the invention but also in the topcoatmaterials, aqueous basecoat materials, and surfacers and antistonechipprimers, are present in the coating material of the inventionadvantageously in an amount of up to 40%, preferably up to 30%, withparticular preference up to 20%, and in particular up to 10%, by weightbased in each case on the solids content of the coating material of theinvention.

[0165] The invention further teaches a process for preparing anabove-described coating material of the invention, in which components(A), (B) and (C) and also, where used, (D) are prepared separately, andwhere components (A), (B) and (C) and also, where used, (D) are mixedand homogenized to give the ready-to-apply coating material. In detail,the component (A) may be prepared as a pigment paste prior to mixingwith components (B) and (C) and also, where used, (D) . Components (A)and (B) and also, where used, (C) are usually prepared in the form ofaqueous dispersions prior to mixing, the dispersion containing component(A) preferably being free from solvents.

[0166] Component (E) may either be admixed to one of components (A), (B)and (C) and also, where used, (D) before these components are mixed, togive a pigment paste, or may be admixed, preferably in the form of apigment paste, to the coating material in the course of the mixing ofcomponents (A), (B) and (C) and also, where used, (D).

[0167] The coating material of the invention is suitable for producingsingle-coat or multicoat coating systems which absorb mechanical energyand/or provide color and/or effect on primed or unprimed substrates. Itis also suitable for producing single-coat or multicoat clearcoatsystems on primed or unprimed substrates or on the single-coat ormulticoat, coating systems which absorb mechanical energy and/or impartcolor and/or effect.

[0168] Suitable substrates include all article surfaces to be coatedwhich are amenable to curing of the paint films present thereon usingheat; that is, for example, articles made of metals, plastics, wood,ceramic, stone, textile, fiber composites, leather, glass, glass fibers,glass wool and rock wool or mineral-bound and resin-bound buildingmaterials, such as plasterboard panels and cement slabs or roofingtiles. Accordingly, the coating material is highly suitable forapplications in automotive finishing the varnishing of furniture, andindustrial coating, including coil coating and container coating. In thecontext of the industrial coatings it is suitable for coating virtuallyall parts for private or industrial use such as radiators, domesticappliances, small metal parts, hub caps or wheel rims.

[0169] The coating material of the invention is especially suitable forproducing paint systems which absorb mechanical energy without beingdestroyed in the process.

[0170] The invention accordingly teaches in particular the use of thecoating material of the invention for producing a surfacer coat and/oran antistonechip primer on a primed or unprimed substrate and also forproducing a coated metallic substrate, preferably a coated motor vehiclebody or a coated motor vehicle body component. In one process forproducing a coated substrate it is preferred if first of all one primer,preferably an electrodeposition primer, is applied to the substrate andbaked and then the coating material of the invention is applied theretoand baked, after which a preferably aqueous basecoat material is appliedand, after flashing off if desired, is optionally overcoated with aclearcoat material, preferably a two-component clearcoat material, and,in the case of overcoating with a clearcoat material, said clearcoatmaterial is baked “wet on wet” together with the basecoat material.

[0171] In this context, the coating material of the invention is appliedin a wet film thickness such that after curing there results in thefinished surfacer coat of the invention or the antistonechip primer ofthe invention a dry film thickness of from 5 to 100, preferably from 10to 75, with particular preference from 15 to 55, and in particular from15 to 40, μm.

[0172] The coating material of the invention may be applied by anycustomary application method, such as spraying, knife coating, brushing,flow coating, dipping or rolling, for example. It is preferred to employspray application methods, such as compressed air spraying, airlessspraying, high-speed rotation, electrostatic spray application (ESTA),alone or in conjunction with hot spray application such as hot airspraying, for example. Applications may be conducted at temperatures ofmax. 70 to 80° Celsius, so that suitable application viscosities areachieved without any change in or damage to the coating material and itsoverspray (which may be intended for reprocessing) occurring during theshort period of thermal stress. For instance, hot spraying may beconfigured in such a way that the coating material is heated only verybriefly in the spray nozzle or shortly before the spray nozzle.

[0173] The spray booth which is used for application may be operated,for example, with an optionally temperature-controllable circulationwhich is operated with a suitable absorption medium for the overspray,an example being the coating material itself.

[0174] The thermal curing also has no special features in terms of itsmethod but instead takes place in accordance with the customary andknown methods such as heating in a forced air oven or exposure to IRlamps. Advantageously, the thermal curing takes place at a temperatureof from 100 to 180° C. and with particular preference from 120 to 160°C. for a time of from 1 min up to 2 h, with particular preference from 2min up to 1 h, and in particular from 3 min to 30 min. Where substratesare used which are able to withstand high thermal loads, thermalcrosslinking may also be conducted at temperatures above 180° C. Ingeneral, however, it is advisable not to exceed temperatures of 180° C.,and preferably not to exceed temperatures of 160° C.

[0175] The surfacer coats or antistonechip primers of the invention havean outstanding, balanced profile of properties in which even divergentproperties such as, for example, very good multiple impact and singleimpact, low film thickness and very good filling power/topcoatappearance, low baking temperature and very good topcoat appearance, andlow baking temperature and high adhesion are realized simultaneously.

EXAMPLES AND COMPARATIVE EXPERIMENT Example 1

[0176] Preparation of a Component A

Example 1.1

[0177] Preparation of a Polyesterpolyol A1

[0178] 492 g of adipic acid, 559 g of isophthalic acid and 1192 g ofhexanediol were weighed into a reactor equipped with stirrer, column andoil heating and were slowly heated to 220° C. The water of reactioneliminated was distilled off from the reaction mixture via a column. Thereaction was continued until an acid number of the solid resin of <5 isreached. The finished polyester has a viscosity of 1.9 dPas measured in70% dilution in butyl glycol.

Example 1.2

[0179] Preparation of a Polyurethane Dispersion A2

[0180] 444 g of 4,4-dicyclohexylmethane diisocyanate (Desmodur W fromBayer), 57 g of dimethylolpropionic acid, 44 g of neopentyl glycol and185 g of N-methylpyrrolidone were weighed into a reactor with stirrer,reflux condenser and oil heating and were heated to 100° C. The NCOgroup content was determined hourly. At an NCO content of 9.74% in thesolution, it was cooled to 85° C. and 1037 g of the polyester describedunder example 1.1 were added. The mixture was reheated to 100° C. andthe reaction was continued with measurement of the NCO content. When theNCO content of the solution was less than 0.2%, it was cooled to 85° C.and 37 g of dimethylethanolamine were added for neutralizing thecarboxyl groups. Then 1900 g of water were added. The resultingpolyurethane dispersion had a solids of 40% (measured in a forced airoven for 60 min at 130° C.), an acid number of 19.2 and a pH of 8.3(measured in 2:1 dilution in water).

Example 2

[0181] Preparation of a Component B

[0182] 631.2 g of a polyesterdiol made from isophthalic acid, dimerfatty acid and hexanediol (number-average molecular weight Mn about1400) and 60.4 g of dimethylolpropionic acid were reacted with 354.4 gof 4,4-dicyclohexylmethane diisocyanate (Desmodur W from Bayer) in 448.2g of ethyl methyl ketone at 80° C. until the NCO content was constant.Then 33.1 g of diethanolamine were added and the reaction mixture washeld at 80° C. with stirring for 2 hours. After the temperature had beenlowered to 60° C., 108.9 g of trimerized hexamethylene diisocyanate(Basonat® HI 100 from BASF) and 54.4 g of methyl ethyl ketoxime wereadded and stirring was continued at 60° C. for 30 minutes. Then afurther 33.1 g of methyl ethyl ketoxime were added. The reaction mixtureis held at 60° C. for 1 hour more and then 20.0 g of diethanolamine and20 g of methyl ethyl ketone are added for chain extension. After theexothermic reaction had subsided, the temperature was held at 80° C.until an NCO content of <0.1% was reached. The product at this point hada cone-and-plate viscosity of 3.0-6.0 dpas, measured in 1:1 dilutionwith N-methylpyrrolidone at 23° C. and 1000 s⁻¹. Then 121 g of butylglycol were added. 70% of the carboxyl groups present were thenneutralized with diethanolamine at 80° C. and 1972 g of distilled waterwere added over the course of one hour, with vigorous stirring, andcomponent (B) was dispersed therein. Thereafter, the methyl ethyl ketonewas distilled off in vacuo and the dispersion was adjusted to a solidscontent of 37%.

Example 3

[0183] Preparation of a Component D

[0184] 442.4 g of hexanediol and 166.6 g of a technical-grade dimericfatty acid (dimer content at least 80%, trimer content not more than20%) were weighed into a reactor equipped with stirrer, column and oilheating and were slowly heated to 130° C. Then a further 184.3 g ofisophthalic acid were added and heating was continued to 220° C. Thewater of reaction eliminated was distilled off from the reaction mixturevia a column. The reaction was continued until an acid number of 10.5 isreached. Following cooling to 140° C., 266.7 g of trimellitic anhydridewere added in portions with stirring. The mixture was then heated to150° C. and subjected to esterification until an acid number of 67.7 hadbeen reached. It was then cooled to 120° C. and diluted with butylglycol so as to give a solution having a solids content of 85%. The 85%polyester solution was heated to 140° C. and admixed in portions with209.6 g of an epoxy resin made from bisphenol A and epichlorohydrin,having an epoxy equivalent weight of 490. Reaction was then carried outat 140° C. until an acid number of 42.1 and an epoxy equivalent of morethan 50 000 had been reached. The product was then cooled to below 100°C. and neutralized with 64.6 g of NN-dimethylethanolamine. The reactionmaterial was then run off with vigorous stirring into 2000 g ofdeionized water which had been heated to 60° C. beforehand. Finally, thedispersion was adjusted to a solids content of 35% and a pH of 7.5.

Example 4

[0185] Preparation of the Pigment Dispersion of an Inventive Surfacer

[0186] 400 g of the polyurethane dispersion described under example 1,7.4 g of Aerosil® R972 (Degussa), 33 g of Bayferrox 3910® (Bayer), 100 gof talc 10MO (TDL), 204 g of Ti-pure® R900 (Du Pont), 26.2 g ofSicomixschwarz® 6190 (BASF), 60 g of Blancfix® N (Sachtleben) and 140 gof deionized water were treated in a dissolver for 30 minutes and thenground to a fineness of 12-15 μm in a commercial bead mill operated incirculation mode. The temperature during grinding was at least 30° C.,maximum 60° C. At least 7 theoretical circuits were run.

Example 5

[0187] Preparation of an Inventive Aqueous Surfacer

[0188] To 970.6 g of the pigment dispersion from example 4 there wereadded 7.6 g of Additol® XW 395 (Vianova Resins), 408 g of the aqueouspolyester described under example 3, 188 g of the aqueous polyurethanedispersion described under example 2, 136 g of a water-dilutablemethanol-etherified melamine resin, 100 g of the aqueous polyurethanedispersion described under example 1, 0.6 g of dimethylethanolamine, 20g of butyl glycol, 20 g of butyl diglycol, 44 g of Byketol® WS (BykChemie) and 45.8 g of deionized water, with stirring. After the finalitem, homogenization was carried out for 1 hour. The composition wasadjusted with dimethylethanolamine to a pH of 7.5 and with deionizedwater to a viscosity of 60-100 s DIN 4 (Ford Cup). For application, aprocessing viscosity of 30 s DIN 4 was set using deionized water.

Example 6

[0189] Preparation of a Pigment Dispersion of an Aqueous Surfacer(Comparative Example)

[0190] 400 g of the aqueous polyester described under example 3., 7.4 gof Aerosil® R972 (Degussa), 33 g of Bayferrox® 3910 (Bayer), 100 g oftalc 10MO (TDL), 204 g of Ti-pure® R900 (Du Pont), 26.2 g ofSicomixschwarz® 6190 (BASF) , 60 g of Blancfix® N (Sachtleben) and 140 gof deionized water were treated in a dissolver for 30 minutes and thenground to a fineness of 12-15 μm in a commercial bead mill operated incirculation mode. The temperature during grinding was at least 30° C.,maximum 60° C. At least 7 theoretical circuits were run.

Example 7

[0191] Preparation of an Aqueous Surfacer (Comparative Experiment)

[0192] To 970.6 g of the pigment dispersion from example 6 there wereadded 7.6 g of Additol® XW 395 (Vianova Resins), 508 g of the aqueouspolyester described under example 3, 188 g of the aqueous polyurethanedispersion described under example 2, 136 g of a water-dilutablemethanol-etherified melamine resin, 0.6 g of dimethylethanolamine, 20 gof butyl glycol, 20 g of butyl diglycol, 44 g of Byketol® WS (BykChemie) and 45.8 g of deionized water, with stirring. After the finalitem, homogenization was carried out for 1 hour. The composition wasadjusted with dimethylethanolamine to a pH of 7.5 and with deionizedwater to a viscosity of 60-100 s DIN 4 (Ford Cup) . For application, aprocessing viscosity of 30 s DIN 4 was set using deionized water.

Example 9

[0193] Test Results

[0194] The coating materials prepared in this way were subjected totests for the properties of surfacer coats produced using them. Theproperties of the surfacer coats were tested in a multicoat systemfamiliar to the skilled worker, which can be produced from a commercialelectrocoat, the inventive aqueous surfacer from example 5 or thecomparative surfacer from example 7, a commercial aqueous basecoatmaterial and a commercial 2K clearcoat material, the aqueous basecoatmaterial and the 2K clearcoat material being applied by the techniqueknown as the wet-on-wet technique without baking in between.

[0195] The results of the tests can be found in the table. TABLE Testresults Properties Example 5 Example 7 Example 9.1: Application of thesurfacer in a film thickness of 20 μm, baking temperature 155° C. Ballshot (material removed in mm)^(a)) 6 8 Multiple impact VDA (rating)^(b))2 2 Topcoat appearance (rating)^(c)) 2 3 Adhesion GT2 (rating)^(d)) 0 2Example 9.2: Application of the surfacer in a film thickness of 35 μm,baking temperature 155° C. Ball shot (material removed in mm)^(a)) 8 13Multiple impact VDA (rating)^(b)) 2 2 Topcoat appearance (rating)^(c)) 23 Adhesion GT2 (rating)^(d)) 0 2

[0196] Comparison of the respective test results shows that only theinventive coating material of example 5 at baking temperatures below160° C. gives a surfacer which passes both the multiple impact and thesingle impact tests with distinction and which even at comparatively lowfilm thickness exhibits very good topcoat appearance and very goodadhesion.

1. A method for making an aqueous coating material comprising: I.forming a water-dispersible binder component that contains groupscomprising urethane groups and blocked isocyanate groups by a methodcomprising: (1) reacting at least one polyol and at least one firstpolyisocyanate to form a polyurethane prepolymer that contains groupscomprising isocyanate groups, (2) reacting the polyurethane prepolymerthat contains groups comprising isocyanate groups with a first chainextender to give a hydroxyl-containing, chain-extended polyurethaneprepolymer, (3) reacting the hydroxyl-containing, chain-extendedpolyurethane prepolymer with at least one second polyisocyanate to givea further polyurethane prepolymer that contains groups comprisingisocyanate groups, and (4) blocking at least a portion of the isocyanategroups of the chain-extended polyurethane prepolymer that containsgroups comprising isocyanate groups with a blocking agent to give apolyurethane that contains groups comprising blocked isocyanate groups,and if there are free isocyanate groups remaining, (5) reactingremaining free isocyanate groups in the polyurethane with a second chainextender; and II. mixing the water-dispersible binder component with (A)a water-dispersible hydroxy-functional binder component that containsgroups comprising urethane groups, (B) a water-dispersible amino resin,(C) optionally, a coatings additive, and (D) optionally, awater-dispersible hydroxy-functional polyester.
 2. The method of claim1, wherein the water-dispersible hydroxy-functional binder component hasan OH number of from 30 to 160 mg KOH/g.
 3. The method of claim 1,wherein the water-dispersible hydroxy-functional binder component has anumber-average molecular weight of from 500 to 20,000.
 4. The method ofclaim 1, wherein the water-dispersible hydroxy-functional bindercomponent comprises a reaction product of at least one polyol having anumber-average molecular weight of from 100 to 5,000 with at least onepolyisocyanate the structure and proportions of the polyol andpolyisocyanate being selected subject to the proviso that thewater-dispersible hydroxy-functional binder component has an OH numberof from 30 to 160 mg KOH/g.
 5. The method of claim 4, wherein the polyolis a polyesterpolyol.
 6. The method of claim 5, wherein thepolyesterpolyol comprises a reaction product of adipic acid, at leastone dimer fatty acid, and hexanediol.
 7. The method of claim 1, whereinthe polyol comprises a reaction product of isophthalic acid, at leastone dimer fatty acid, and hexanediol.
 8. The method of claim 1, whereinthe polyol has a number-average molecular weight of from 1,000 to 2,000.9. The method of claim 1, wherein the first polyisocyanate and thesecond polyisocyanate are each independently at least one of adiisocyanate adduct that contains at least one isocyanurate group and adiisocyanate.
 10. The method of claim 1, wherein the blocking agent isan oxime.
 11. The method of claim 1, wherein the amino resin is amelamine-formaldehyde resin that is reactive toward OH groups attemperatures of from 100° C. to 180° C.
 12. The method of claim 1,wherein the water-dispersible hydroxy-functional polyester comprises atleast in part an epoxy-resin-modified, water-dilutable polyestercomprising a reaction product of i) a polyester and ii) an epoxy resinin an amount from 0.3 to 1.5 equivalents per polyester molecule, (D1)wherein the polyester comprises a reaction product of (D1.1) one of atleast one polycarboxylic acid that contains groups comprising at leastthree carboxyl groups and at least one reactive derivative of thispolycarboxylic acid, and (D1.2) optionally, at least one polyol thatcontains groups comprising at least one carboxyl group and (D1.3) one ofat least one polycarboxylic acid that contains groups comprising twocarboxyl groups, and at least one reactive derivative of thispolycarboxylic acid, and (D1.4) at least one polyol, wherein instructural units of a combined amount of (D1.1), (D1.2), (D1.3) and(D1.4) comprises at least 10 mol % of at least one (cyclo)aliphaticstructural element comprising at least six carbon atoms, wherein thepolyester has a number-average molecular weight of less than 2,000, anacid number of from 35 to 240 mg KOH/g, an OH number of from 56 to 320mg KOH/g, and in which all (D1.1) and (D1.3) are incorporated bycondensation via at least two carboxyl groups; (D2) wherein the epoxyresin comprises at least one of (D2.1) an epoxy resin that has anepoxide equivalent weight of from 170 to 1,000 and is based on abisphenol and (D2.2) a derivative of this epoxy resin that contains atleast one epoxide group per molecule; wherein, in the reaction,substantially only carboxyl groups react with epoxide groups to give anepoxy-resin-modified polyester, and wherein at least a portion of freecarboxyl groups are neutralized such that the water-dispersiblehydroxy-functional polyester is water-dilutable.
 13. The method of claim1 further comprising applying one coat of the coating material to aprimed or unprimed substrate.
 14. The method of claim 13, wherein thecoat is at least one of a surfacer coat, an antistonechip coat, a colortopcoat, an effect topcoat, a color and effect topcoat, an aqueousbasecoat, and a clearcoat, and wherein the at least one coat is anenergy-absorbing paint system.
 15. The method of claim 1, wherein atleast two of: I. the water-dispersible hydroxy-functional bindercomponent has an OH number of from 30 to 160 mg KOH/g; II. thewater-dispersible hydroxy-functional binder component has anumber-average molecular weight of from 500 to 20,000; III. thewater-dispersible hydroxy-functional binder component comprises areaction product of at least one polyol having a number-averagemolecular weight of from 100 to 5,000 with at least one polyisocyanatethe structure and proportions of the polyol and polyisocyanate beingselected subject to the proviso that the water-dispersiblehydroxy-functional binder component has an OH number of from 30 to 160mg KOH/g; IV. the polyol comprises a reaction product of isophthalicacid, at least one dimer fatty acid, and hexanediol; V. the polyol has anumber-average molecular weight of from 1,000 to 2,000; VI. the firstpolyisocyanate and the second polyisocyanate are each independently atleast one of a diisocyanate adduct that contains at least oneisocyanurate group and a diisocyanate; VII. the blocking agent is anoxime; VIII. the amino resin is a melamine-formaldehyde resin that isreactive toward OH groups at temperatures of from 100° C. to 180° C.;and IX. the water-dispersible hydroxy-functional polyester comprises atleast in part an epoxy-resin-modified, water-dilutable polyestercomprising a reaction product of i) a polyester and ii) an epoxy resinin an amount from 0.3 to 1.5 equivalents per polyester molecule, (D1)wherein the polyester comprises a reaction product of (D1.1) one of atleast one polycarboxylic acid that contains groups comprising at leastthree carboxyl groups and at least one reactive derivative of thispolycarboxylic acid, and (D1.2) optionally, at least one polyol thatcontains groups comprising at least one carboxyl group and (D1.3) one ofat least one polycarboxylic acid that contains groups comprising twocarboxyl groups, and at least one reactive derivative of thispolycarboxylic acid, and (D1.4) at least one polyol, wherein instructural units of a combined amount of (D1.1), (D1.2), (D1.3) and(D1.4) comprises at least 10 mol % of at least one (cyclo)aliphaticstructural element comprising at least six carbon atoms, wherein thepolyester has a number-average molecular weight of less than 2,000, anacid number of from 35 to 240 mg KOH/g, an OH number of from 56 to 320mg KOH/g, and in which all (D1.1) and (D1.3) are incorporated bycondensation via at least two carboxyl groups; (D2) wherein the epoxyresin comprises at least one of (D2.1) an epoxy resin that has anepoxide equivalent weight of from 170 to 1,000 and is based on abisphenol and (D2.2) a derivative of this epoxy resin that contains atleast one epoxide group per molecule; wherein, in the reaction,substantially only carboxyl groups react with epoxide groups to give anepoxy-resin-modified polyester, and wherein at least a portion of freecarboxyl groups are neutralized such that the water-dispersiblehydroxy-functional polyester is water-dilutable.
 16. The method of claim15 further comprising applying one coat of the coating material to aprimed or unprimed substrate.
 17. The method of claim 16, wherein thecoat is at least one of a surfacer coat, an antistonechip coat, a colortopcoat, an effect topcoat, a color and effect topcoat, an aqueousbasecoat, and a clearcoat, and wherein the at least one coat is anenergy-absorbing paint system.